Vacuum units

ABSTRACT

A vacuum unit for an ignition distributor includes a housing which is divided internally into first and second chambers by a diaphragm. A connecting link for attachment at one end to the timing plate of the ignition distributor is connected at its other end to the diaphragm so as to move therewith. Secured to the housing of the unit is a bracket whereby the unit can be secured in position on the casing of the ignition distributor and the bracket is provided with a locating member. In use the locating member is engaged by the detachable insulating cap of the distributor, and so serves to locate the cap angularly in the desired position relative to the distributor casing. The connecting link is provided at said one end with means whereby the connecting link is coupled to the timing plate. Said connecting means is provided on the link by a shaping operation, and the position of said means is determined using the location member of the bracket as a reference point.

' Jukes [451 Dec. 17, 1974v 1 1 VACUUM UNITS Norman Alfred Jukes,Walsall, England [75] Inventor:

[73] Assignee: Joseph Lucas (Electrical) Limited,

Birmingham, England [22] Filed: Jan. 15, 1973 [21] Appl. No.: 323,362

[30] Foreign Application Priority Data Primary ExaminerCharles .1. MyhreAssistant Examiner-Ronald B. Cox Attorney, Agent, or Firm-Holman & Stern[5 7] ABSTRACT A vacuum unit for an ignition distributor includes ahousing which is divided internally into first and second chambers by adiaphragm. A connecting link for attachment at one end to the timingplate of the ignition distributor is connected at its other end to thediaphragm so as to move therewith. Secured to the housing of the unit isa bracket whereby the unit can be secured in position on the casing ofthe ignition distributor and the bracket is provided with a locatingmember. In use the locating member is engaged by the detachableinsulating cap of the distributor, and so serves to locate the capangularly in the desired position relative to the distributor casing.The connecting link is provided at said one end with means whereby theconnecting link is coupled to the timing plate. Said connecting means isprovided on the link by a shaping operation, and the position of saidmeans is determined using the location member of the bracket as areference point.

4 Claims, 3 Drawing Figures VACUUM UNITS This invention relates tovacuum units for internal combustion engine spark; ignition systemignition; distributors and to a method of manufacturing such units.

A vacuum unit according to the invention includes a housing dividedinternally into first and second chambers by a diaphragm, a connectinglink secured at one end to the diaphragm and extending from the firstchamber for connection, in use, to the timing plate of an ignitiondistributor, and a bracket secured to the housing and whereby the unitcan be secured in position on the casing of an ignition distributor, thebracket being provided with a locating member engageable, in use, by thedetachable insulating cap of the distributor, so as to locate the capangularly in the desired position on the distributor casing.

Preferably the bracket is so shaped as to permit two alternativepositions of the unit relative to the casing of the distributor, oneposition providing clockwise rotation of the timing plate of thedistributor as the connecting link is withdrawnby the unitin use, andthe second position. providing anti-clockwise rotation of the timingplate as the connecting link is withdrawn in use, the bracket beingprovided with a 'pair of location members for the distributor cap one ofthe pair being operative in said one'position of the bracket and theother of the pair being operative in the second position of the bracket.I

Conveniently the bracket is detachably secured to the distriburor casingby means of screws.

The invention further resides in a method of manufacturing a vacuum unitincluding a housing divided internally into first andsecond chambers bya diaphragm,

a connecting link secured at one end tothe diaphragm and extending fromthe first chamber for connection in use to the timingplate of adistributor, and a mounting bracket provided with a locating member forlocating, in use, the distributor cap, the method including performing ashaping operation to provide on the connect- One example of theinvention is illustrated in the accompanying drawings wherein:

FIG. 1 is a perspective view of an ignition distributor with partsthereof omitted for clarity,

FIG. 2 is a sectional view of the vacuum unit shown in FIG. 1, and

HO. 3 is a view in the direction of arrow A in FIG. 2.

Referring to the drawings, the ignition distributor includes a hollowmetal casing 11 within which is journalled a 'cam shaft (not shown).Supported within the casing is a contact breaker assembly (not shown)part of which is angularly movable about the axis of the cam shaft inthe usual manner to effect alteration in the ignition timing of thedistributor. Engageable with the casing 11 of the distributor is aninsulating cap 12 which when in position closes the casing 11, and whichcarries a centrally disposed high tension input terminal 13 and aplurality of generally equi-angularly spaced high tension outputterminals 14. The cam shaft carries at its upper end a rotor arm whichis permanently electrically connected to the input high tension terminal13, and which rotates with the cam shaft of the distributor todistributehigh tension sparking pulses to the output terminals 14 in turn.

Secured to the casing 11 is a vacuumunit 15 which controls adjustment ofthe angular position of the contact breaker assembly of the distributorin the usual ing link means whereby the link can be coupled to thedistributor timing plate in use, the shaping operation being performedafter assembly of the unit and the position, on the link, at which saidmeans is provided being determined utilizing the location member of thebracket as'a reference point. 1

Desirably said means is a hole in the link through which in use a pinextends to connect the link to the distributor timing plate.

In a further aspect the invention resides in an ignition distributor foruse in the spark ignition system of an internal combustion engine, thedistributor including, a hollow casing, a contact breaker assemblymounted for angular adjustment within the casing, a vacuum unit securedto the casing, through the intermediary of a bracket, the unit includinga connecting link connecting a diaphragm of the unit to said contactbreaker assembly, and an insulating cap closing said casing and carryinghigh tension terminals of the distributor, the bracket of the vacuumunit being provided with a location member which mates with theinsulating cap to locate the cap angularly with respect to the casing.

Preferably the periphery of the casing which engages the cap is unbrokenas permitted by the provision of the cap location on the bracket.

formed from two pressed steel parts inter-connected at theirperipheries. Trapped between the peripheries of the pressed steel partsof the housing 16 is the periphery of a flexible diaphragm 17 whichdivides the housing internally into first and second chambers. Securedto the diaphragm l7, and extending through the wall of the first chamberis a connecting link 18, and positioned within the second chamber andalso secured to the diaphragm is a plunger 19. Acting between thediaphragm l7 and the wall of the second chamber is a spring 21 whichurges the diaphragm 17 to move in a direction to reduce the volume ofthe first chamber. A connecting union 22 is provided on the wall of thesecond chamber whereby the second chamber can be placed in communicationwith a source of vacuum. The first chamber is open to atmosphere, and soas the pressure within the second chamber is reduced then the diaphragm17 and accordingly the plunger 19 and connecting link 18 are movedagainst the action of the spring 21.

Secured to the wall of the first chamber of the housing 16 is a mountingbracket 23. The mounting bracket 23 is also formed as a metal pressing,and is shaped to engage the cylindrical outer surface of the casing 11of the distributor. The casing of the distributor is provided with anaperture through which the connecting link 18 extends, and at its endsthe bracket 23 is provided with holes 24 for the reception of fixingscrews. The con-- necting link 18 is provided adjacent its free end witha pierced hole 25 through which, in use, extends a pin carried by themovable part of the contact breaker assembly. Thus the connecting link18 couples the diaphragm 17 of the vacuum unit to the movable part ofthe contact breaker assembly, so that as the diaphragm l7 moves inaccordance with fluctuations in pressure in the second chamber of theunit.l5 then the contact breaker assembly is moved angularly to adjustthe ignition timing of the distributor in accordance with the pressurefluctuations. In the conventional manner, the

second chamber of the vacuum unit communicates with the inlet manifoldof the internal combustion engine utilising the ignition distributor.

As previously stated, the bracket 23 is shaped to engage the cylindricalouter surface of the casing 11. The axis of the vacuum unit is notradially disposed with respect to the curvature of the bracket 23, andso the connecting link l8 extends within the casing 11 of thedistributor adjacent the inner wall of the casing. It will beappreciated, that the vacuum unit can be engaged in two alternativepositions with the casing 11. Considering the distributor in plan view,the vacuum unit 15 can be engaged in a first position so that withdrawalof the connecting link moves the contact breaker assembly clockwise(FIG. 1) and alternatively, by rotating for.

As with conventional ignition distributors, it is essential that whenthe cap 12 and casing 11 are engaged,

then the capl2 and accordingly the terminals 14 are in predeterminedangular positions with respect to the casing 11 and the componentscarried by the casing. In order to locate the cap 12 in the correctposition with respect to the casing 11 the bracket 23 is provided withan upstanding locating member 26 which projects upwardly, and which isreceived in a corresponding recess 27 in the inner wall of the cap 12.In order to locate the cap 12 in a direction transverse to the axis ofthe distributor the casing 11 is provided with a circumferentialshoulder 11a and an upstanding wall 11b having an external diametersubstantially equal to the internal diameter of the cap 12. Since thelocating member 26 is provided on the bracket 23 then the shoulder 11aand the wall 11b can be unbroken, so enhancing the resistance of thejunction between the cap and the casing, to ingress of contaminants.

Since the bracket 23 is arranged, as described above to provide twoalternative mounting arrangements, then the bracket 23 is formed with asecond locating member 28 which is not in use, in the arrangement shownin FIG. 1. However, it is to be appreciated that in an anti-clockwisedistributor the location member 28 it would engage the cap 12 and thelocation member 26 would not be in use.

When the vacuum unit 15 is assembled, the free end of the connectinglink 18 is left plain. Thus the whole of the unit including the bracket23 is assembled, and with the diaphragm 17 in a rest position to whichit is urged by the spring 21, the hole 25 is pierced in the end of theconnecting link 18. The piercing operation is the last operation whichis performed on the vacuum unit. and the position of the hole 25 in thelink 18 is determined using the location member 26 as a fixed referencepoint. Thus the hole 25 is pierced in the connecting link 18 at apredetermined distance from the locating member 26 with the diaphragm 17in its rest position, and so tolerances involved in the manufacture ofthe vacuum unit are not incorporated in the positioning of the hole 25in relation to the locating member 26. This feature is of particularimportance in that it minimises the build up of tolerance errors withinthe ignition distributor. Since the hole 25 and the locating member 26are accurately positioned with respect to one another, then the cap 12and of course the terminals 14 of the cap 12, will be accuratelypositioned relative to the hole 25. The hole, as previously described,receives a pin whereby the connecting link 18 is coupled to the contactbreaker assembly of the distributor and so the cam follower of thecontact breaker assembly will accurately be positioned relative to theterminals 14. The cam shaft of the distributor engages the cam followerand at certain points known conveniently as break points the cam causesthe contacts of the contact breaker assembly to open thereby causinggeneration of a sparking pulse which is supplied by way of the terminal13 of the cap 12 to the movable high tension electrode of a rotor armcarried by the cam shaft. The path of rotation of the electrode as thecam shaft rotates takes the electrode close to the terminals 14 in turn.When a sparking pulse is generated it is conducted by the electrode tothe nearest terminal at that instant and it will be appreciated thatconventional distributorshave sufficient accuracy to ensure that theterminals 14 receive sparking pulses in the desired sequence. However toensure this the electrode of the rotor arm requires to have a relativelylarge arcuate length and also to avoid the possibility of distributionof the pulse to the wrong terminal 14, the angular spacing between theterminals 14 is relatively large thus necessitating a cap of largediameter.

In the present example, as described above,the heel of the contactbreaker assembly is positioned relative to the terminals 14 with minimalinaccuracy owing to tolerances, and since the rotor arm is carried bythe cam shaft, the electrode thereof is positioned accurately relativeto the break point of the cam shaft. Thus the overall accuracy of thedistributor is increased in such a manner that the necessary arcuatelength of the rotor electrode is reduced and the spacing needed betweenthe terminals 14 is also reduced, the reduction in terminal spacingleading to a reduction in the necessary diameter of the cap 12.

The housing 16 and bracket23 of the vacuum unit described above areformed from metal pressings. However, it is to be appreciated that thesecomponents can be formed also by die-casting techniques. Moreover, thearrangement has been described as being secured to the casing of thedistributor by a pair of screws. It is to be appreciated that othersecuring means can be provided, and in an arrangement where it is notdesired to provide the facility of replacing the vacuum unit then thebracket 23 could be welded or otherwise permanently secured to thecasing. In the arrangement where screws are used to secure the bracket23 to the casing l 1 it is convenient to provide on a fixed mountingplate of the contact breaker assembly a pair of tags between which isreceived the shank of one of the fixing screws for the bracket 23, thefixing screw constituting a stop to resist rotation of the mountingplate within the casing of the distributor.

Additionally the use of one or other of the fixing screws to locate themounting plate facilitates assembly of the distributor since therequired orientation of the plate relative to the casing is immediatelyapparent to the operator assembling the distributor.

Onescrew will provide the plate location in an anticlockwise distributorand the other screw will provide the location in a clockwisedistributor.

I claim;

l. A vacuum unit (as claimed in claim 1 wherein), for an ignitiondistributor, including a housing divided internally into first andsecond-chambers by a diaphragm, a connecting link secured at one end tothe diaphragm and extending from the first chamber for connection, inuse, to the timing plate of an ignition distributor, and a bracketsecured to the housing and whereby the unit can be secured in positionon the casing of an ignition distributor, the bracket (is) being soshaped as to permit two alternative positions of the unit relative tothe casing of the distributor, one position providing clockwise rotationof the timing plate of the distributor as the connecting link iswithdrawn by the unit in use, and the second position providnganti-clockwise rotation of the timing plate as the connecting link iswithdrawn in use, the bracket being provided with a pair of locationmembers one or other of which is engageable, in use, by the detachableinsulating cap of the distributor so as to locate the cap angularly inthe desired position on the distributor casing, (for the distributorcap) oneof the pair being operative in said one position of the bracketand the other of the pair being operative in the second position of thebracket.

2. A vacuum unit as claimed in claim 1 wherein the bracket is detachablysecured to the distributor casing by means of screws.

3. An ignition distributor including a hollow casing, a contact breakerassembly mounted for angular movement within the casing, a vacuum unitsecured to the casing through the intermediary of a bracket the unitincluding a connecting link connecting a diaphragm of the unit to saidcontact breaker assembly, and an insu' lating cap closing said casingand carrying high tension terminals of the distributor, the bracket ofthe vacuum unit being (provided with a location member which mates withthe insulating cap to locate the cap angularly with respect to thecasing.) so shaped as to permit two alternative positions of the unitrelative to the casing of the distributor, one position providingclockwise rotation of the timing plate of the distributor as theconnecting link is withdrawn by the unit in use, and the second positionproviding anti-clockwise rotation of the timing plate as the connectinglink is withdrawn in use, the bracket including a pair of locationmembers one or other of which is engaged with said insulating cap of thedistributor so as to locate the cap angularly in the desired position onthe distributor casing, one of said pair of location members beingoperative in said one position of the bracket, and the other of the pairbeing operative in the second position of the bracket.

cap location on the bracket.

1. A vacuum unit (as claimed in claim 1 wherein), for an ignitiondistributor, including a housing divided internally into first andsecond chambers by a diaphragm, a connecting link secured at one end tothe diaphragm and extending from the first chamber for connection, inuse, to the timing plate of an ignition distributor, and a bracketsecured to the housing and whereby the unit can be secured in positionon the casing of an ignition distributor, the bracket (is) being soshaped as to permit two alternativE positions of the unit relative tothe casing of the distributor, one position providing clockwise rotationof the timing plate of the distributor as the connecting link iswithdrawn by the unit in use, and the second position providnganti-clockwise rotation of the timing plate as the connecting link iswithdrawn in use, the bracket being provided with a pair of locationmembers one or other of which is engageable, in use, by the detachableinsulating cap of the distributor so as to locate the cap angularly inthe desired position on the distributor casing, (for the distributorcap) oneof the pair being operative in said one position of the bracketand the other of the pair being operative in the second position of thebracket.
 2. A vacuum unit as claimed in claim 1 wherein the bracket isdetachably secured to the distributor casing by means of screws.
 3. Anignition distributor including a hollow casing, a contact breakerassembly mounted for angular movement within the casing, a vacuum unitsecured to the casing through the intermediary of a bracket the unitincluding a connecting link connecting a diaphragm of the unit to saidcontact breaker assembly, and an insulating cap closing said casing andcarrying high tension terminals of the distributor, the bracket of thevacuum unit being (provided with a location member which mates with theinsulating cap to locate the cap angularly with respect to the casing.)so shaped as to permit two alternative positions of the unit relative tothe casing of the distributor, one position providing clockwise rotationof the timing plate of the distributor as the connecting link iswithdrawn by the unit in use, and the second position providinganti-clockwise rotation of the timing plate as the connecting link iswithdrawn in use, the bracket including a pair of location members oneor other of which is engaged with said insulating cap of the distributorso as to locate the cap angularly in the desired position on thedistributor casing, one of said pair of location members being operativein said one position of the bracket, and the other of the pair beingoperative in the second position of the bracket.
 4. An ignitiondistributor as claimed in claim 3 wherein the periphery of the casingwhich engages the cap is unbroken as permitted by the provision of thecap location on the bracket.